Related to 0241c71a4c

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/3270#issuecomment-2143782962

With this change, it should be possible for people to adjust the Docker
dependency from `docker.service` to something else (e.g. `pkg-ContainerManager-dockerd.service`),
or to completely eliminate it by setting `devture_systemd_docker_base_docker_service_name` to an empty string.

This makes it easier for people to use the playbook against a Synology DSM server.

commit cf8637efac
Author: Slavi Pantaleev <slavi@devture.com>
Date:   Sun Mar 24 19:14:57 2024 +0200

    Make devture_systemd_docker_base_ipv6_enabled automatically reconfigure geerlingguy/ansible-role-docker

    Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/3218

commit dc7af3bc7d
Author: Slavi Pantaleev <slavi@devture.com>
Date:   Sun Mar 24 19:10:31 2024 +0200

    Replace matrix_ipv6_enabled with devture_systemd_docker_base_ipv6_enabled

    Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/3218

commit 07e900d6a2
Author: Slavi Pantaleev <slavi@devture.com>
Date:   Sun Mar 24 19:01:51 2024 +0200

    Improve matrix_ipv6_enabled comments

commit 3f03ca7f69
Author: Tilo Spannagel <development@tilosp.de>
Date:   Sat Mar 9 19:27:50 2024 +0000

    Add setting to enable ipv6

Signed-off-by: gardar <gardar@users.noreply.github.com>

Most of these files were defining a service, usually toward the end.
These lines have been moved upward.

Some components (mautrix-signal, mautrix-gmessages, etc.) were defining
a service conditionally (only if metrics are exposed, etc). This was
causing issues like these in the Traefik logs:

> level=error msg="service \"matrix-mautrix-twitter\" error: port is missing" providerName=docker container=matrix-mautrix-twitter-..

This moves the comments from being just in Jinja,
to actually ending up in the generated `labels` file,
which makes inspection of the final result easier.

Also, some new lines were added here and there to make labels
more legible.

The generated file may still include weird new-lines due to
various `if` statements yielding content or not, but that's not so ugly
anymore - now that we have proper start/end sections that are visible in
the final `labels` file.

This is an attempt at optimizing service startup.

The effect is most pronounced when many services are restarted one by one.
The systemd service manager role sometimes does this - for example when `just install-service synapse` runs.
In such cases, a 5-second delay for each Synapse worker service
(or other bridge/bot service that waits on the homeserver) quickly adds up to a lot.

When services are all stopped fully and then started, the effect is not so pronounced, because
`matrix-synapse.service` starts first and pulls all worker services (defined as `Wants=` for it).
Later on, when the systemd service manager role "starts" these worker services, they're started already.
Even if they had a 5-second wait each, it would have happened in parallel.

* one var to control encryption across all bridges

* move var to matrix-base

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/2427

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/2427

`metrics_enabled` should only expose the metrics locally, on the
container network, so that a local Prometheus can consume them.

Exposing them publicly should be done via a separate toggle (`metrics_proxying_enabled`).
This is how all other roles work, so this makes these mautrix roles consistent with the rest.

We expect `--tags=start` to handle systemd reloading, so we don't need
to do it manually each time we install/uninstall a .service file.

- forego removing Docker images - it's not effective anyway, because it
  only removes the last version.. which is a drop in the bucket, usually

- do not reload systemd - it's none of our business. `--tags=start`,
  etc., handle this

- combine all uninstall tasks under a single block, which only runs if
  we detect traces (a leftover systemd .service file) of the component.
  If no such .service is detected, we skip them all. This may lead to
  incorect cleanup in rare cases, but is good enough for the most part.

This was useful when the order of these roles in relation to Synapse
mattered (when we were injecting stuff into Synapse variables during
runtime). This is no longer the case since 0ea7cb5d1812a88, so all of
this can be removed.

This paves the way for installing other roles into `roles/galaxy` using `ansible-galaxy`,
similar to how it's done in:

- https://github.com/spantaleev/gitea-docker-ansible-deploy
- https://github.com/spantaleev/nextcloud-docker-ansible-deploy

In the near future, we'll be removing a lot of the shared role code from here
and using upstream roles for it. Some of the core `matrix-*` roles have
already been extracted out into other reusable roles:

- https://github.com/devture/com.devture.ansible.role.postgres
- https://github.com/devture/com.devture.ansible.role.systemd_docker_base
- https://github.com/devture/com.devture.ansible.role.timesync
- https://github.com/devture/com.devture.ansible.role.vars_preserver
- https://github.com/devture/com.devture.ansible.role.playbook_runtime_messages
- https://github.com/devture/com.devture.ansible.role.playbook_help

We just need to migrate to those.